A USB to powerline bridge is a network device that instead of using an ordinary Ethernet cable (CAT5 for example) or wireless LAN it uses the powerlines as a network to communicate with similar devices.
A more comprehensive explanation of what it is and how it works you can find here.

It is assumed you use a static IP, otherwise you can just use your DHCP client to get an unused IP address from your DHCP server. Setting up the interface is done like this (change the IP address and netmask accordingly if it's different):